Question

The element which is not common between the compounds called baking soda and soda ash is
(a) sodium
(b) hydrogen
(c) oxygen
(d) carbon

Answer 1

(b) hydrogen
Washing soda (soda ash), Na₂CO₃ contains Na, C and O, whereas baking soda, NaHCO₃, is made up of Na, C, H and O. So, the element, which is not common in the two, is hydrogen.